1. Field of the Invention
The present invention relates to an image display device, and more specifically relates to an image display device which displays an image at a repeatedly rewritable image display medium which, by the application of voltages, moves colored particles between support plates for displaying the image.
2. Description of the Related Art
Heretofore, as repeatedly rewritable image display mediums with memory characteristics, image display mediums which employ colored particles (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2001-312225) and image display mediums which employ electrophoresis (see, for example, JP-A No. 2004-45976) have been known. Such an image display medium has a structure which includes, for example, a pair of plates (substrates) and particle groups of a number of varieties differing in color and electrostatic polarity, which are sealed between the plates to be movable between the plates by applied electric fields. Hence, the particles are moved by the application of voltages, which correspond to an image, between the pair of plates, and the image is displayed.
“Simple matrix driving” may be employed as a driving system of such an image display medium. In simple matrix driving, positions of intersection between, for example, a number of linear row electrodes provided at a display plate side of the image display medium and a number of linear column electrodes provided at a rear face plate side, which are perpendicular with the row electrodes, serve as pixel positions. Voltage is sequentially applied by a common driver IC to the column electrodes, which serve as scan electrodes, and, contemporaneously therewith, voltage is sequentially applied with a segment driver IC to the row electrodes, which serve as data electrodes, in accordance with a line image corresponding to the column electrode to which voltage is applied. Thus, an image is displayed.
At the common driver IC and the segment driver IC, the scanning directions of the electrodes are usually specified in advance. Thus, circuit structures are simplified and costs are reduced, and stable circuits with high output capabilities are structured.
Now, in an image display medium which employs colored particles as described above, a speed of response of the colored particles is slow, and when a line image corresponding to a column electrode that has been selected by the common driver is written by the row electrodes being sequentially scanned by the segment driver IC, a long scanning time is required, in comparison with liquid crystal devices. For example, a scanning time for a colored particle display medium is 1 to 10 ms/line, compared with 0.01 to 0.5 ms/line for a liquid crystal device. Accordingly, when a number of scanning lines is increased in order to raise resolution of images, the time to complete scanning of each frame is correspondingly lengthened. As a result, a user viewing the image display medium will be aware of directions of progress of scanning (in particular, a direction of sub-scanning) as directions of changes in rewriting of images.
A direction of reading of a document is generally determined by the document. For example, an English document is written horizontally from left to right, a Japanese document is written vertically from top to bottom, and an Arabic document is written horizontally from right to left. Directions of reading of information will also vary in accordance with arrangements of images, tables and the like.
A common driver IC and segment driver IC or the like which are employed in a liquid crystal device are structured such that scanning proceeds in essentially predetermined scanning directions. Consequently, scanning is always conducted in the same direction, regardless of details such as which direction the contents of the display will be read in. Hence, because a state of progress of scanning is more obvious with a display medium which employs colored particles than with liquid crystals or the like, a very irritating effect will be produced when, for example, scanning proceeds in the vertical direction during reading of a horizontally written document. This is not confined only to rewriting of display contents. An observer will also feel a sense of wrongness at a time of re-display for refreshing a display state.
Further, when a horizontally long display medium is turned to the left by 90° for use in a vertically long manner, if the medium has, for example, circuit structure such that a scanning direction sequentially scans toward the right before this rotation, scanning will be performed from bottom to top after the rotation, and a viewer's sense of wrongness will be greatly reinforced. In such circumstances, changing the driver IC, to which a large number of wires are connected, each time the orientation is changed would be difficult.
Accordingly, a display device which enables viewing by a viewer of a display medium employing colored particles without any sense of oddness, regardless of details of displays, orientation and the like, has been desired.